Bacterial spores are generally accepted to be indicator species for validating sterility since they are the most resilient form of life against sterilization regimens. Traditional bacterial spore analysis is a labor intensive and time consuming process. For example, spore analysis may involve heat activation, serial dilution, plating on a suitable growth medium, and incubation for two to three days until enumeration can be performed. This analysis process can take several days, requiring manufacturers of product undergoing analysis to hold significant quantities of the product before receiving sterility test results that allow them to release product to the marketplace. Moreover, in instances where there is a sterility issue, the lack of real-time information can result in several days' worth of production being deemed out of specification and needing to be discarded or repurposed.
In an attempt to provide faster analysis, designers have utilized optical analysis techniques that detect optical emission signals associated with bacterial spores and then correlate these signals with spore count. These techniques are of limited use, however, for many categories of materials desirably analyzed for bacterial spore count. For example, materials that contain a low number of bacterial spores or contain bacterial spores within a surrounding fluid that optically interferes with the emissions associated with the spores can be difficult to evaluate using optical analysis techniques. As one example, dairy production facilities monitoring bacterial spore counts in their products typically cannot use optical emission analysis techniques. This is because proteins and other molecules within the dairy products can optically interfere with emissions produced by bacterial spores.